1. Field of the Invention
This invention relates to a protective cylinder for a pipe covering material. The invention is particularly applicable to a cylindrical protective tube for protectively covering the periphery of a covering material such as a heat insulating material located on an outer surface of a pipe for airconditioning piping arranged on the interior and/or exterior of a building. Such a protective cylinder is formed into a predetermined length and mounted on the covering material, an appropriate number of protective cylinders being used depending upon the length of the pipe. The cylinders are connected together through fittings between the upper and lower ends of vertically adjacent cylinders in situ.
2. Description of the Prior Art
A conventional protective cylinder will be described with reference to FIGS. 11 to 13.
FIG. 11 is a fragmentary enlarged sectional view showing part of a fitted connection between conventional protective cylinders, connected together;
FIG. 12 is a perspective view showing another conventional protective cylinder system in position; and
FIG. 13 is a fragmentary enlarged sectional view showing part of a connection between the protective cylinders of FIG. 12, connected together.
A conventional protective cylinder generally designated by reference numeral 3 in FIG. 11 is formed by folding one longitudinal edge 3a of a rectangular blank plate (such as a tin plate) twice, to provide a folded section and to form inwardly and outwardly open slits 4a and 4b and an outside bent portion 4c at the edge. The tip of the edge is bent inwardly to form an inside holding rim 5, and the opposite longitudinal edge 3b of the blank plate is pressed to form the edge with step-like stoppers 6 which project inwardly from an inner surface of the edge and are arranged at equal intervals in the longitudinal direction of the blank plate.
A modification of this system is constructed as shown in FIGS. 12 and 13. In the modification, upper sections of portions of both edges 3a and 3b which are respectively folded and provided with the stoppers 6 are cut away to eliminate the slits 4a and 4b and the stoppers 6, thereby forming cut-outs 7 and 8 of a small rectangular shape.
Arrangement of the protective cylinder 3 of FIG. 11 on the outer periphery of a covering material is carried out by mounting, on the covering material, the number of protective cylinders 3 required depending on the length of the pipe on which the covering material is arranged and connecting the protective cylinders 3 to each other in turn in situ.
Fixing of each of the protective cylinders 3 on the covering material is carried out by bending the protective cylinder 3 around the outer periphery of the covering material to fit the former on the latter and then inserting the opposite longitudinal edge 3b into the outwardly open slit 4b of the longitudinal edge 3a to engage step-like stopper 6 with the inside holding rim 5 by means of the elasticity of the protective cylinder 3.
A plurality of the protective cylinders 3 are each fixed on the pipe in a continuous length as described above, and the protective cylinders 3 are connected to one another through their upper and lower ends in turn. The connection between adjacent protective cylinders 3 constructed as described above is carried out by fitting a lower end portion of an upper side protective cylinder 3' on an upper end portion of a lower-side protective cylinder 3" while slightly contracting the upper end of the lower side protective cylinder 3".
However, the lower-side protective cylinder 3" shown in FIG. 11 lacks any means for facilitating insertion of its upper end portion into the lower end portion of the upper-side protective cylinder 3'. Thus, it is necessary to insert the outside bent portion 4c of the lower-side protective cylinder 3" bent to define the inwardly open slit 4a forcibly and overlappingly into the inwardly open slit 4a of the upper-side protective cylinder 3' while at the same time forcing the opposite longitudinal edge 3b of the lower-side protective cylinder 3" provided with the stoppers 6 into the outwardly open slit 4b of the upper-side protective cylinder 3' while enlarging the slits 4a and of the upper side protective cylinder 3'. This results in the connecting operation being troublesome, requiring much time and effort. Additionally the protective cylinders connected together are unsightly due to the enlargement of the overlapped connection portions.
The protective cylinder system shown in FIGS. 12 and 13 eliminates some of the above disadvantages of the system shown in FIG. 11. Particularly, the cut-outs 7 and 8 which are provided at the upper ends of the edges 3a and 3b of the protective cylinder 3 to form the upper end of the cylinder 3 into a simple cylindrical shape, so that fitted connection between the upper-side and lower-side protective cylinders 3' and 3" may be readily carried out by merely fitting the upper portion of the lower side protective cylinder 3" in the lower end portion of the upper side protective cylinder 3'. Also, abutment of the longitudinal edges 3a of both protective cylinders 3' and 3" against each other in a manner to align the outside bent portions 4c of the cylinders with each other considerably improves the unshapeliness of the connected cylinders of FIG. 11.
Nevertheless, the protective cylinder 3 FIGS. 12 and 13 fails to enable the initial fitting between adjacent upper-side and lower-side protective cylinders to be carried out smoothly because the cut-outs 7 and 8 are merely formed into a small rectangular shape.
Furthermore, the protective cylinder of FIGS. 12 and 13 permits the outside bent portions 4c of the connected cylinders 3' and 3" to be linearly aligned with one another at a final step after each connection. However, the upper end of the protective cylinder 3 is formed into a cylindrical shape due to existence of the cut-outs 7 and 8 as described above. This shape causes the lower side protective cylinder 3" to be readily rotatable with respect to the upper side protective cylinder, 3', so that it is substantially impossible to keep the outside bent portions 4c linearly aligned with each other. This still leads to unshapeliness of the connected protective cylinders.
For example, when the protective cylinder is used to cover pipes tens of meters or more in length which are located in noticeable locations on a building, a substantial failure in alignment of the outwardly bent portions 4c deteriorates the appearance of the connected cylinders.